The medical home model is a team-based approach to primary care that includes and utilizes all health team members in the delivery of patient care, promoting each to work to the top of his/her license and training. However, current evaluation measures and studies have largely focused on the performance of primary care providers (PCPs; physicians, nurse practitioners, and physician assistants), and have failed to adequately capture the activities of associate care providers (ACPs; nurses, pharmacists, social workers, and dieticians). This longitudinal retrospective study will assess the distribution and trend of primary care clinical encounters delivered by ACPs across five years, and will test whether ACP involvement in encounters are associated with medical home implementation and access to care and utilization outcomes. Almost 900 primary care sites nationwide within the Veterans Health Administration will be included in analyses. Results will inform clinical management and policies that delineate the roles and responsibilities of interdisciplinary team members in providing patient encounters, as well as documentation of such care activities. Furthermore, this work will create a measure of ACP involvement in patient encounters that can inform a standardized measure for use across health services research and medical home evaluations.